PROJECT SUMMARY This research investigates the mechanisms by which protein ubiquitination regulates cellular resistance to oxidative stress in neuronal cells. Oxidative stress is a very prominent type of stress induced by exposure to diverse environmental factors, such as ionizing radiation, heat, and pollutants, which can damage biomolecules and result in cellular death. Increased exposure to oxidants combined with the accumulation of toxic protein aggregates is the leading cause of several neurodegenerative diseases such as Parkinson?s and Alzheimer?s. To prevent cell death and disease progression, cells use a variety of defense mechanisms, which includes the modification of proteins by ubiquitin. Ubiquitination is the canonical signal for removing damaged and un-needed proteins through the proteasome, but we recently characterized a new function for K63 ubiquitin in translational control in yeast. However, the role of this ubiquitin pathway in higher eukaryotes is completely unknown. Here we will 1) use large scale proteomics approaches to identify the K63 ubiquitin sites in neuronal cells and study their roles during the progression of the translation cycle, and 2) characterize the role for the K63 ubiquitin enzymes in cellular response to stress. This research will unravel novel mechanisms to increase cell tolerance to stress depending on selective ubiquitination. Our unique approach combines systems-wide methodologies with molecular biology and genetic tools to decode the complexity of ubiquitination signals in response to stress. Understanding the multiple ubiquitin roles in cellular response to stress and the specificity of each distinct pathway will provide groundbreaking insights into innovative strategies for treatment and early diagnosis of many stress-related disorders.